Compression-rheostat.



E. L. CLARK.

COMPRESSION RHEOSTAT.

APPLICATION FILED MAY 31, 1912.

1,143,810. Patented June 22, 1915.

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WITNESSES INVENTOR MW EM RSON L..CL.ARK

WMK BY /Q ad ATTORNEY E. L. CLARK.

COMPRESSION RHEOSTAT.

APPLICATION FILED MAY3I, I912.

1 1 43 ,8 1 O. I Patented June 22, 1915.

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WITNESSES INVENTOR EMERSON LLCLIARK ATTORNEY Patented June 22, 1915.

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COMPRESSION RHEOSTAT APPLICATION FILED MAY31| 1912.

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INVENTOR EMERSON L. CLARK Q10 9. M m

' ATTORNEY PIG-.51.

WITNESSES STATES PATENT ormcn.

mason L. cmx, or LAKEWOOD, OHIO,-ASSIGITOR TO mirroimr. cannon 0012mm,

] CLEVELAND, OHIO, A CORPGRATION OF NEW JERSEY.

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Toall who-m, itma' 'concern: V Be it known that I, EMERSON L. CLARK, a resident of Lakewood, in the county of Cuyaho'ga, in the State of Ohio, have invented new and useful Improvements in Compression-Rheostats, of which the following is a clear and exact description.

This invention relates to rheostats of the compression type in'which the resistor. elements consist of carbon, graphite or mixtures of these substances with other materials. However, the invention is not limited to the use of anyspecific materials,

and. hence may embrace resistors "composed of any materials.

One object of my invention is to construct a rheostat withreadily replaceable resistor units each having means rigidly attached thereto for radiating the heat.

Another object is to construct a rheostat with slight frictional resistance to movement atingplate.

so that the elements when compressed or released from pressure will all move in unison.

Other objects will appear in the appended description. 4

Referring to the figures, Figure 1 is an end view of a resistor element. Fig. 2 is a plan view of the element shown in Fig. 1. Fig. 3is a plan view of the radiating plate before the carbon or composition blocks are attached thereto. Fig. 4 is a sectional view of the radiating plate taken on the line A -A of Fig. 3; Fig. 5 is a sectional view of the radiating plate takenon the line B B of Fig. 3. Fig. 6 is a sectional view of the resistor element and radiating plate taken on the line CC of'Fig. 2. Fig; 7 is a sectional view of a modification showing a resistor element having only one composition block. Fig. 8 is a plan view of another modification in which the composition blocks are arranged at one side of the radi- Fig. 9 is an end view of another modification. Fig. 10 is a' plan view of the resistor element shown in Fig. 9. Fig.

11 is a sectional view of the resistor element taken on the line D--D of Fig. 10.

modification similar to that shown in Figs 9, '10, and 11 in which a gnaze radiating plate is usedJFig. 14 is a sectional view of-atheresistor element taken on the line of Fig. 13. Fig. 15 a modification which the composition blocks are ce- Specification of Letters Patent. Patented June 22, 1915, Application filed Kay 31, 1912. Serial No. 700,558.

mented to the radiating plate. Fig. 16 is a modification arranged for radiating 'heat without the use of separate heat conducting plates. Fig. 17 is a plan view of one of the blocks shown in Fig. 16. Fig. 18 is an end view of a modification similar to Fig. 16. Fig. 18 is a modified form of resistance block. Fig. 19 is a modification in which the radiating plate is cast in grooves in the composition blocks. Fig. 20 is an isometric .view of the composition blocks of Fig. 19 be fore the plate is cast therein. Fig. 21 is an end riew of the modification shown in Fig. 20 with the grooves arranged parallel. Fig. 22 isa modification showing a resistor consisting of one block with a radiating plate cast in grooves therein. Fig. 23 is a side elevation of a rheostat in which the resistor elements are used. Fig. 24 is a plan view of the rheostat shown in Fig-23. Fig. 25 is an elevation of the endvplates of the rheostat shown in Figs. 23 and 24. Fig. 26 is a modification of Figs. 23 and 24 in which the resistor element is suspended on parallel bars. Fig. 27 is a partial sectional view of the point of support of the screw rod against the end plate. Fig. 28 is a partial sectional view of another modification for communicating pressure. Fig. 29 is another modified form of block. Fig. 30 is a modified form of rheostat. Fig. 31 is a section on F-F of Fig. 30.

Referring to Figs. 3, 4 and 5, lugs l are punched in a plate 3 so as to extend on one side thereof. These alternate with lugs 2 punched so as to extend on the other side of the plate. Composition blocks 4 are then placed betweenathe lugs, one on each side of the plate. The lugs are then firmly pressed against or into the composition blocks as is shown in Fig. 6. This arrangement provides for a very rigid resistor having a radiating plate in good contact with the sides of the composition blocks. a

In order to prevent the metal from oxidizing and producing anundesirable resistance atthe contact surface, the metal plate is coated with some metal that will not only one block in connection with each radiating plate.

In Fig. 8 a modification is shown in which the composition block or blocks are placed near one edge of the radiating plate. The advantage of this arrangement will be explained later.

In Figs. 9, 10, 11 and 12 a modification is shown in which the composition materials are pressed into and through holes 5 in the radiating plate 3, as shown in Fig. 12. The holes punched in the radiating plate may be of various-shapes and sizes and the arrangement of the holes'may be varied as desired. The plate and composition material properly mixed with a suitable binder are placed in a mold and put under hydraulic or other pres sure which forces the material in intimate contact with the parts of the radiating plate wires in the gauze plate in the same manner as has been described in modification in Figs. 10, 11 and 12. The cross section of this type of resistor element is shown in Fig. 14.

In Fig; 15 the composition blocks are either brazed or cemented to the radiating plate 3. The brazing material or conducting cement is shown at 4, the thickness being exaggerated somewhat to make the construction clear. When the blocks are to be brazed to the plate they are first coated on one side with copper or other metal and then the plating is joined to the plate by brazing in the usual manner. When the blocks are cemented to the plate they need not be copper coated. Conducting cements are well known 4 in the art, and as a typical example the following may be given: 100 parts graphite, 40 parts bronze powder and enough glucost or sugar and water to make a stiff paste. The paste can be applied to either the plate or the resistor and the two parts pressed together in proper relation. They are then hacked to a sufficient temperature to carbonize the glucose or sugar. After baking it will be found that the cement is conductive and will firmly join the resistor to the plate. The shape of the blocks and plate in Fig. 15 is the same as is shown in prior fig ures with the exception that the plate has no notched lugs.

In Fig. 16 an arrangement is shown whereby provision is made for getting rid of the heat without the use of metallic plates. The composition blocks 7 have corrugations 8 extending along the sides of the blocks as shown in Figs. 16, 17 and 18. These blocks are placed with the corrugations extending vertically so that there will be a circulation of air between the blocks. The heat is readily dissipated by the circulation of air grooves may be of various shapes. In Fig.

18 slightly different shaped grooves are shown. In Fig. 18 the grooved surfaces are placed in contact. The holes 8 are for the purpose of suspending the plates in a rheostat as described later.

In Figs. 19 and 20 the composition blocks 4 have undercut corrugations or grooves extending across one side. The blocks are placed in a proper mold with the grooved surfaces in contact or closely adjacent and with the grooves of the one block running approximately at right angles to those of the other, and molten metal is poured in .so that it will entirely fill all the grooves in the plate and form a rediating plate 9 as shown in Fig. 19. The mold, of course, will be arranged in well known ways so that this plate can be cast. It is obvious that the plates shown in Figs. 19 and 22 as well as those in the other figures, may be square, circular or any other shape. The blocks need not be necessarily arranged with the grooves at right angles. They may be arranged at various angles or they may be parallel. Fig. 21 shows the latter arrangement. The preferable arrangement, however, is with the grooves approximately at right angles. The material used for casting may be iron, copper, zinc, aluminum or any other metal or alloy. The material may be cast in the blocks by pressure casting well known in the art.

In Fig. 22 a resistor is shown consisting of only one block with undercut grooves and a radiating plate cast therewith.

Referring to Fig. 23, a rheostat is shown in which the resistor elements are used. End plates 10,11 are joined at the corners by four rods 12.properly fastened by the nuts 13. The shape of the plates and the arrangement of the holes is shown in Fig. 25. The holes 14 receive the rods 12. In the center a plate 14:, somewhat similar to plates 10 and 11, is fastened rigidly to-the rods 12 by screws 15 or by other appropriate means. Insulated rods 16 pass loosely through holes 17 in the plates 10, 11 and 14:

and are fastened at each end of the rheostat magic and24issimilartothatshowninFig.8-,in

which the composition blocks are at or near the top of the radiating plate. The blocks may be secured in any of the ways disclosed herein. Each resistor element is supported on the lower rods 12 by means of 7 its radiating plate as shown in lines in Fig. 25.

"End plates 24; 25 are placed at each en of the rheostat. These plates must be rigid enough to transmit the pressure uniformly over the surface of the composition blocks when applied through the screw 20 and pin 23. The end plates are preferably largerthan the resistor blocks so asto have additional surface for radiating heat as is shown in the figures. The end plates are supported by the 'lower rods 12 in the same manner as are the resistor elements. The lower parts of the end plates and of the radiating plates of the resistor elements admit of conductors being clamped thereto and hence the elements may be arranged in parallel groups if desired. As'shown in Fig. 23, theterminals 26 and 27 are clamped to the mentsare in series.

In order to prevent any of the elements from being short circuited the rods 12 and 16 may be covered with transits tubing .or any other electrical insulating and heat insulating material as is shown in section at 28 in Fig. 26. It will be understood that insulating bushings and washers will be used where the rods are joined to the end plates 10 and 11, as is indicated in Figs. 23 and 25 by the parts shown in solid black. The holes 22 in the end plates Y10 and 11 should be properly insulated by bushings 29 as is shown in Fig. 25. The insulation suggested is only one of many ways in which the short circuit may be prevented. Anyone skilled in the art could provide for properly insu lating the parts, and hence these need not be gone into in detail.

The screw 20 should press against the plate 26 through a pointor ball contact as is shown in Fig. 27. If. the screw presses against a flat surface the rotative movement of the screw will cause the plate to reciprocate sidewise and produce undesirable fluctuations in the resistance of the rheostat.

- In Fig. 28 another arrangement is shown whereby the end plate is not caused to move sidewise. Sockets are formed inthe plate 24 and the screw 20 which contain a hardened ball 30. The ball may have a retainer to prevent it from dropping out of the screw 20. The terminals 26 and 27 are shown connected to the end plates 2 1 and 25 so that the current traverses the composition blocks 4, the radiating plates, and the metallic plate 14 in series. By rotating the wheel 21-, the screw 20 forces the resistor elements on the .is twicethat of the other.

rheostat of twice the length and obtain equal plate 14. The reaction transmitted through rods, 16 presses the pin 23 against the plate 25 and compresses the resistor elements on 'the right hand side of the rheostat against the metal plate 14'. If the pile is compressed from one side only so that it would he, say inch shorter than it originally was, the first block on the moving end of the pile would move inch, and the succeeding blocks would move progressively less tances. If the pile is compressed from both ends asin applicants case the two outside blocks would move only ;1 inch and the succeeding ones progressively less. Hence to obtain'the same resistance the average distance of movement of the blocks in one ty e In order to obtain gradual and uniform variation of resistance the movement must be uniformly transmitted through the entire pile. It is evident therefore, that the changes of resistance should be obtained with as small movement of the blocks as possible. The arrangement shown in Figs. 23 and 24 provides for such reduced movement. I end plates'24 and 25so that all of the ele- If the resistor elements are compressed only from one side it takes a certain amount of movement of the first resistor block-before pressure is transmitted to. the last block,

and hence at the first movements of the compression screwv the last blocks will furnish a high contact resistance so that very un Y satisfactory results will be obtained when ,the pressure is first applied and when it is 1 about to be removed. The relatively short compression rheostat therefore gives better results than a long one.- By providing pressure at both ends I am enabled to use a efficiency.

Since the resistor elements are supported on the rods 12' by means of radiating plates they pivot at the point of support and move about the pivotal point under compression 1 and on release of pressure. This reduces the frictional resistance and hence the resistor -elementsmove readily and provide for uniform variation of resistance. If the composition blocks were placed at the bottom 115 of the radiating-plates or near the middle,

the mechanical resistance caused by the plates sliding along the rods 12 would preventthe elements om moving readily, and the variations of resistance would be irregular, especiall at the point of maximum resistancefi 0 course, when the blocks are placed at the top of the radiating plates there will still be some sliding of the plates along the rods 12 at the pivotal points, but 1 the movement is reduced, and by making the plates of suflicient size the movement will be ne ligible.

Fig. 26 an arrangement is shown where the blocks are fastened to the base. of the no sistor elements pivoting on the bearing rodsin aisimilar manner to that'previously described.

In Fig. 29 another form or resistance block is shown. Holes 32 extend through the block to promote cooling by means of air currents... The blocks would be arranged in the rheostat with the holes vertical.

In Figs. 30 and 31 a modified form of rheostat is shown. Insulation boards 32, made for instance of transit are fastened to the end plates 33, and extend on both sides of the resistance blocks. The blocks are thus inclosed on four sides and-a chimney effect is produced whereby a draft is caused, indicated by the arrows 34, when the blocks are heated by the current traversing them. The end plates 33 are shown extending below the sides 32 so that the rheostat. can be placed on a table or floor without impairing the circulation of the air...' Inthis type the blocks ofFigs. 16, 18 or 18 are suspended by a wire 35 which extends through two holes 8 and engages hooks 36 supported in notches 37 in the transit boards. This arrangement is very simple and on account of the flexibility of the wires the blocks move without any friction whatever. The remaining details of the rheostat are similar to those in Figs. 23 and 24. The block shown in Fig. 29 may also be suspended in a rheostat in the same way by passing wires 35 through the holes 32. The rheostat shown in Fig. 23 may be inclosed by boards similarly to the arrangement shown in Fig. 31.

Having described my invention what I claim is:

1. In electric rheostats, a resistor element consisting of a block of carbonaceous material and having channels for conducting a cooling fluid.

2. In electric rheostats, a resistor element consisting of a block having grooves ex tending along the surface of one side.

3. A pile rheostat consisting of a series of carbon blocks having a plurality of channels for the circulation of cooling fluid.

4. In electric rheostats, a plurality of double-faced resistor plates arranged in a pile, a plurality of 'orrugations in the faces of each plate wl reby a plurality. of channels are formed by the adjacent corrugations for conducting a cooling fluid.

5. A rheostat consisting of a series of blocks of carbonaceous material, an inclosure for the blocks having openings for admitting and removing a cooling fluid whereby a circulation of said fluid is produced when the blocks become heated.

7. In an electric rheostat, end plates, side pieces joining said end plates to form an inclosure, resistance blocks suspended between the side pieces and spaced therefrom to rovide for the circulation ofa cooling flui 8. In an electric rheostat, end members, side pieces joining said members, a block secured to the side pieces between the end members, resistors suspended between the side pieces and means for compressing the resistors from both ends of the rheostat.

- 9. In a rheostat having end plates, side plates cooperating therewith to form an inclosure, a plurality of resistance blocks in said inclosure, two flexible supporting means for each block, spaced apart and connected thereto, said means also being connected to the side plates and means extending through one of the end plates to apply pressure to the resistance blocks.

10. In a rheostat'having end plates, side plates cooperating therewith to form an inclosure, a stationary member intermediate to the end plates and cooperating with the side plates to divide the inclosure into two compartments, a'plurality of-resistance blocks in each compartment, two flexible supporting means for each block, spaced apart and connected thereto, said means also being connected to the side plates, and means ex:

tending through each of the end plates to apply pressure to the resistance blocks'in each compartment.

11. A rheostat having resistance blocks, a support for said blocks and flexible, nonresilient means for pivotally suspending the 

